1. Field of the Invention
The present invention relates to a pattern inspecting apparatus and a pattern inspecting method for inspecting a minute or fine pattern of a semiconductor memory such as a DRAM having memory cells formed in an array shape on a wafer and a mask to be used for manufacturing the wafer.
2. Prior Art
There has been disclosed a conventional minute or a fine pattern inspecting apparatus in, for example, Japanese Patent Application Laid-open No. 61-200415. FIG. 1 is a block diagram for showing the conventional minute pattern inspecting apparatus similar to the apparatus disclosed in the publication. In FIG. 1, a reference numeral 410 denotes an image processing and a system control unit, 412 an image memory, 413 an image processing auxiliary unit, 414 an auxiliary image memory, 415 an image display circuit, 416 a display, 417 a stage control circuit, 421 a light source, 423 a CCD image sensor, 441 an XY stage, 445 a specimen to be inspected, 451 an irradiation beam, 452 a reflected beam, and 453 an image signal.
In this example, a general optical beam is used instead of an electron beam source for the light source. Referring to FIG. 1, this apparatus includes the image processing and system control unit 410, the light source 421 as a beam irradiating unit for generating an image, the CCD image sensor 423 as a detector, the image memory 412 for storing the image signal 453 by having an input of this image signal, the image processing auxiliary unit 413, the auxiliary image memory 414 for storing a normal inspection pattern, the image display circuit 415, the display 416 for displaying a result of an inspection, the XY stage 441 for moving the specimen to be inspected 445, and the stage control circuit 417 for controlling the XY stage.
An inspection of a minute pattern by this apparatus is performed in the following manner. The irradiation beam 451 is irradiated onto the specimen to be inspected 445 on the XY stage 441 from the light source 421 for generating an image. The reflected beam 452 having image information such as a surface shape or the like of the specimen to be inspected 445 is detected by the CCD image sensor 423. The image signal 453 obtained from the CCD image sensor 423 is stored in the image memory 412. The image processing and system control unit 410 extracts a defect on the specimen to be inspected 445 by comparing image information obtained through the image processing auxiliary unit 413 and normal inspection pattern data prepared separately and called from the auxiliary image memory 414.
The image processing and system control unit 410 further calculates a position of a defect based on the above information and information of a stage position obtained from the stage control circuit 417, and displays on the display 416 a position of the defect on the specimen to be inspected 445 through the image display circuit 415.
The conventional minute or fine pattern inspecting apparatus shown in FIG. 1 has the following problems.
At First, at the time of comparing the inspection data pattern with the pattern obtained from the specimen to be inspected, it is necessary to match an image position for recognizing the pattern, taking a relatively long time for the calculation. Further, for carrying out a pattern recognition in high accuracy, it is necessary to move the stage in high accuracy. As a result, the apparatus tends to be larger in size, making it relatively difficult to perform a rapid move of the stage. Moreover, as the comparison operation is carried out in one image frame unit, a large amount of memories are required, leading to a large-size apparatus.